A method for producing a hot-rolled h-shaped steel of russian standard 355mpa

Abstract

This invention discloses a method for producing Russian standard 355MPa hot-rolled H-beams, comprising: hot metal desulfurization → converter smelting → LF refining → continuous casting of shaped billets → slow cooling of billets → walking beam furnace heating → high-pressure water descaling → BD roughing and rolling → universal roughing and finishing rolling → controlled cooling → slow cooling on a cooling bed → straightening → sawing → inspection and warehousing. The chemical composition by weight percentage is: C: 0.12-0.18%; Si: 0.20-0.50%; Mn: 1.20-1.60%; P≤0.030%; S≤0.025%; Alt: 0.020-0.050%; Nb: 0.020-0.040%; Ti: 0.010-0.025%; the balance being Fe and unavoidable impurities. The purpose of this invention is to provide a method for producing Russian standard 355MPa hot-rolled H-beams with precise composition, stable process, uniform microstructure, low cost, and full-process compliance.

Description

Technical Field

[0001] This invention belongs to the field of hot-rolled steel manufacturing technology, and particularly relates to a method for producing Russian standard 355MPa hot-rolled H-beams. Background Technology

[0002] Russian standard 355MPa grade H-beams are widely used in construction, bridges, and mechanical structures, requiring a yield strength ReL ≥ 355MPa, tensile strength Rm = 490–630MPa, elongation after fracture A ≥ 21%, and impact energy at room temperature ≥ 27J. Dimensional tolerances and surface quality must strictly match the Russian standard series specifications (20B1–70B2, 20Ш1–70Ш2, 20K1–40K5). Current production often suffers from problems such as redundant composition, poor matching of rolling temperature and cooling, uneven microstructure, large performance fluctuations, high costs, and insufficient compliance with Russian standards. Summary of the Invention

[0003] In order to overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for producing Russian standard 355MPa hot-rolled H-beams with precise composition, stable process, uniform structure, low cost, and full compliance throughout the entire process, ensuring that mechanical properties and dimensional accuracy are consistently up to standard.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a method for producing Russian standard 355MPa hot-rolled H-beams. The production process is as follows: hot metal desulfurization → converter smelting → LF refining → continuous casting of special-shaped billets → slow cooling of billets → walking beam furnace heating → high-pressure water descaling → BD billet rolling → universal roughing rolling + universal finishing rolling → controlled cooling → slow cooling on a cooling bed → straightening → sawing → inspection and warehousing. The key feature is the control of critical processes.

[0006] Smelting and refining:

[0007] Hot metal pretreatment: S≤0.010%;

[0008] Converter: final carbon content ≤ 0.18%, tapping temperature 1640-1680℃, slag-blocking tapping;

[0009] LF refining: white residue is maintained for ≥15 minutes, composition is finely adjusted, and calcium treatment is used to modify inclusions to ensure cleanliness and castability.

[0010] Continuous casting of irregularly shaped billets:

[0011] Full protection during pouring, with a ladle temperature of 1520-1560℃;

[0012] With proper secondary cooling water distribution, the surface of the cast billet is free of cracks, depressions, and segregation;

[0013] The cast billets are stacked and slowly cooled for ≥24 hours after being removed from the production line to release internal stress.

[0014] Heating regime:

[0015] Preheating section ≤950℃; heating section 1180-1260℃; soaking section 1220-1250℃;

[0016] Bake temperature 1130-1170℃; furnace time 150-210min, ensuring thorough homogenization and avoiding overheating;

[0017] Rolling process:

[0018] Descaling: High-pressure water descaling after furnace exit, pressure ≥18MPa, to remove iron oxide scale;

[0019] BD billet preparation: rolling at 1120-1160℃, total reduction rate of 40-55%, to ensure deformation penetration;

[0020] Universal rolling: roughing rolling at 980-1050℃; finishing rolling at 880-930℃, with a cumulative reduction rate of ≥60%, to achieve grain refinement and uniform microstructure.

[0021] Controlled cooling and slow cooling:

[0022] After finishing rolling, laminar / air mist cooling is adopted, with a cooling rate of 3-8℃ / s and a reddening temperature of 650-730℃.

[0023] After air cooling to ≤150℃, straighten the surface to prevent deformation and residual stress.

[0024] Finishing and Inspection:

[0025] Straightening, length sawing, and surface cleaning;

[0026] Batch-by-batch testing of tensile strength, impact strength, dimensions, and surface finish is required to meet GOST R 57837-2017 and GOST 19281-2014.

[0027] The chemical composition of the H-beams by weight percentage is as follows: C: 0.12-0.18%; Si: 0.20-0.50%; Mn: 1.20-1.60%; P≤0.030%; S≤0.025%; Alt: 0.020-0.050%; Nb: 0.020-0.040%; Ti: 0.010-0.025%; N≤0.012%; the balance is Fe and unavoidable impurities. Design considerations: low carbon content ensures weldability; manganese solid solution strengthening; niobium-titanium refines grains and precipitation strengthening; low phosphorus and sulfur content improves toughness and resistance to lamellar tearing; aluminum final deoxidation controls nitrogen content.

[0028] Product performance meets the following requirements:

[0029] Yield strength ReL: 355-390 MPa;

[0030] Tensile strength Rm: 490-610MPa;

[0031] Elongation after fracture (A): 22-28%;

[0032] Impact energy at room temperature KV2: ≥30J.

[0033] Furthermore, the chemical composition of the H-beam by mass percentage is: C 0.15%, Si 0.35%, Mn 1.45%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%; the balance is Fe and unavoidable impurities.

[0034] Furthermore, the chemical composition of the H-beam by mass percentage is: C 0.14%, Si 0.32%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.041%; the balance is Fe and unavoidable impurities.

[0035] Furthermore, the chemical composition of the H-beam by mass percentage is: C 0.16%, Si 0.35%, Mn 1.49%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%; the balance being Fe and unavoidable impurities.

[0036] Furthermore, specifically:

[0037] Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes;

[0038] Rolling: initial rolling at 1140℃, final rolling at 900℃;

[0039] Cooling: Cooling rate 5℃ / s, reddening temperature 690℃;

[0040] Performance: ReL=365MPa, Rm=515MPa, A=24.5%, KV2=39J.

[0041] Furthermore, specifically:

[0042] Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes;

[0043] Rolling: Final rolling temperature 895℃;

[0044] Cooling: Returns to red at 680℃;

[0045] Performance: ReL=360MPa, Rm=505MPa, A=23.5%, KV2=45J.

[0046] Furthermore, specifically:

[0047] Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes;

[0048] Rolling: initial rolling at 1140℃, final rolling at 900℃;

[0049] Cooling: Cooling rate 5℃ / s, reddening temperature 690℃;

[0050] Performance: ReL=368MPa, Rm=535MPa, A=23%, KV2=47J.

[0051] Furthermore, the chemical composition of the H-beam by mass percentage is: C 0.17%, Si 0.31%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.037%; the balance being Fe and unavoidable impurities.

[0052] Furthermore, specifically:

[0053] Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes;

[0054] Rolling: Final rolling temperature 895℃;

[0055] Cooling: Returns to red at 680℃;

[0056] Performance: ReL=363MPa, Rm=522MPa, A=24%, KV2=55J.

[0057] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0058] 1. Precise matching of composition and process: Low-carbon microalloying achieves 355MPa strength, good toughness, and weldability at low cost;

[0059] 2. Temperature-deformation synergistic control: uniform heating, stable final rolling and cooling windows, uniform microstructure, and small performance fluctuations;

[0060] 3. Full-process compliance with Russian standards: dimensions, surface finish, and mechanical properties consistently meet GOST R 57837-2017 and GOST 19281-2014;

[0061] 4. Smooth production: Thorough descaling, stable rolling load, and reasonable cold control reduce cracks, warping, and steel jamming, resulting in a high yield. Detailed Implementation

[0062] The present invention will be further described in detail below with reference to typical embodiments.

[0063] Example 1: Specification 30K

[0064] Composition (wt%): C 0.15%, Si 0.35%, Mn 1.45%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%, the remainder being Fe and impurities;

[0065] Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes;

[0066] Rolling: initial rolling at 1140℃, final rolling at 900℃;

[0067] Cooling: Cooling rate 5℃ / s, reddening temperature 690℃;

[0068] Performance: ReL=365MPa, Rm=515MPa, A=24.5%, KV2=39J at room temperature, meeting Russian standards.

[0069] Example 2: Specification 40B2

[0070] Composition (wt%): C 0.14%, Si 0.32%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.041%, the remainder being Fe and impurities;

[0071] Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes;

[0072] Rolling: Final rolling temperature 895℃;

[0073] Cooling: Returns to red at 680℃;

[0074] Performance: ReL=360MPa, Rm=505MPa, A=23.5%, KV2=45J at room temperature, dimensions and surface meet Russian standards.

[0075] Example 3: Specification 30K

[0076] Composition (wt%): C 0.16%, Si 0.35%, Mn 1.49%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%, the remainder being Fe and impurities;

[0077] Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes;

[0078] Rolling: initial rolling at 1140℃, final rolling at 900℃;

[0079] Cooling: Cooling rate 5℃ / s, reddening temperature 690℃;

[0080] Performance: ReL=368MPa, Rm=535MPa, A=23%, KV2=47J, meets Russian standard.

[0081] Example 4: Specification 40B2

[0082] Composition (wt%): C 0.17%, Si 0.31%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.037%, the remainder being Fe and impurities;

[0083] Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes;

[0084] Rolling: Final rolling temperature 895℃;

[0085] Cooling: Returns to red at 680℃;

[0086] Performance: ReL=363MPa, Rm=522MPa, A=24%, KV2=55J at room temperature, dimensions and surface meet Russian standards.

[0087] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing Russian standard 355MPa hot-rolled H-beams, comprising the following process flow: hot metal desulfurization → converter smelting → LF refining → continuous casting of shaped billets → slow cooling of billets → walking beam furnace heating → high-pressure water descaling → BD billet rolling → universal roughing rolling + universal finishing rolling → controlled cooling → slow cooling on a cooling bed → straightening → sawing → inspection and warehousing; characterized in that: Key process control: Smelting and refining: Hot metal pretreatment: S≤0.010%; Converter: final carbon content ≤ 0.18%, tapping temperature 1640-1680℃, slag-blocking tapping; LF refining: white residue is maintained for ≥15 minutes, composition is finely adjusted, and calcium treatment is used to modify inclusions to ensure cleanliness and castability. Continuous casting of irregularly shaped billets: Full protection during pouring, with a ladle temperature of 1520-1560℃; With proper secondary cooling water distribution, the surface of the cast billet is free of cracks, depressions, and segregation; The cast billets are stacked and slowly cooled for ≥24 hours after being removed from the production line to release internal stress. Heating regime: Preheating section ≤950℃; heating section 1180-1260℃; soaking section 1220-1250℃; Bake temperature 1130-1170℃; furnace time 150-210min, ensuring thorough homogenization and avoiding overheating; Rolling process: Descaling: High-pressure water descaling after furnace exit, pressure ≥18MPa, to remove iron oxide scale; BD billet preparation: rolling at 1120-1160℃, total reduction rate of 40-55%, to ensure deformation penetration; Universal rolling: roughing rolling at 980-1050℃; finishing rolling at 880-930℃, with a cumulative reduction rate of ≥60%, to achieve grain refinement and uniform microstructure; Controlled cooling and slow cooling: After finishing rolling, laminar / air mist cooling is adopted, with a cooling rate of 3-8℃ / s and a reddening temperature of 650-730℃. After air cooling to ≤150℃, straighten the surface to prevent deformation and residual stress. The chemical composition of the H-beams by weight percentage is as follows: C: 0.12-0.18%; Si: 0.20-0.50%; Mn: 1.20-1.60%; P≤0.030%; S≤0.025%. Alt: 0.020-0.050%; Nb: 0.020-0.040%; Ti: 0.010-0.025%; balance is Fe and unavoidable impurities; Product performance meets the following requirements: Yield strength ReL: 355-390 MPa; Tensile strength Rm: 490-610MPa; Elongation after fracture (A): 22-28%; Impact energy at room temperature KV2: ≥30J.

2. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 1, characterized in that: The chemical composition of the H-beam by weight percentage is: C 0.15%, Si 0.35%, Mn 1.45%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%; the balance is Fe and unavoidable impurities.

3. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 1, characterized in that: The chemical composition of the H-beam by weight percentage is: C 0.14%, Si 0.32%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.041%; the balance is Fe and unavoidable impurities.

4. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 1, characterized in that: The chemical composition of the H-beam by weight percentage is: C 0.16%, Si 0.35%, Mn 1.49%, P 0.022%, S 0.018%, Nb 0.028%, Ti 0.016%, Alt 0.032%; the balance is Fe and unavoidable impurities.

5. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 2, characterized in that: Specifically: Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes; Rolling: initial rolling at 1140℃, final rolling at 900℃; Cooling: Cooling rate 5℃ / s, reddening temperature 690℃; Performance: ReL=365MPa, Rm=515MPa, A=24.5%, KV2=39J.

6. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 3, characterized in that: Specifically: Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes; Rolling: Final rolling temperature 895℃; Cooling: Returns to red at 680℃; Performance: ReL=360MPa, Rm=505MPa, A=23.5%, KV2=45J.

7. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 4, characterized in that: Specifically: Heating: 1150℃ after removal from the oven, then in the oven for 180 minutes; Rolling: initial rolling at 1140℃, final rolling at 900℃; Cooling: Cooling rate 5℃ / s, reddening temperature 690℃; Performance: ReL=368MPa, Rm=535MPa, A=23%, KV2=47J.

8. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 1, characterized in that: The chemical composition of the H-beam by weight percentage is: C 0.17%, Si 0.31%, Mn 1.40%, P 0.025%, S 0.020%, Nb 0.030%, Ti 0.018%, Alt 0.037%; the balance is Fe and unavoidable impurities.

9. The method for producing Russian standard 355MPa hot-rolled H-beams according to claim 8, characterized in that: Specifically: Heating: 1145℃ after exiting the furnace, then in the furnace for 190 minutes; Rolling: Final rolling temperature 895℃; Cooling: Returns to red at 680℃; Performance: ReL=363MPa, Rm=522MPa, A=24%, KV2=55J.